The [Incendiary Grenades] technology could instead give the [Grenadier] a charged ability where they will occasionally throw or launch an incendiary grenade that will cause a fire when hitting the ground, which will spread out to a certain radius and last there for a limited amount of time, thus damaging any enemy unit that continues to be inside of this fire.
In other words, what I am suggesting is that the [Grenadier] could have the ability to deal area denial damage with the [Incendiary Grenades] technology.
I made a post last year where I suggested that the [Mortar], [Monitor] and their other counterparts could have an area denial ability through researching a new technology called the “Carcass Shot” that would be available from the [Arsenal] building and through other means for non-European civilisations.